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Re: [Xen-devel] [PATCH] xen/arm64: Don't zero BSS when booting using EFI
Hi Jan, On 03/02/17 07:41, Jan Beulich wrote:
On 02.02.17 at 20:25, <julien.grall@xxxxxxx> wrote:@@ -261,6 +265,8 @@ GLOBAL(init_secondary) sub x20, x19, x0 /* x20 := phys-offset */ mov x22, #1 /* x22 := is_secondary_cpu */ + /* Skip zero BSS on secondary CPUs to avoid nasty surprises. */ + mov x26, #1 /* X26 := skip_zero_bss */ common_start: mov x24, #0 /* x24 := CPU ID. Initialy zero until we @@ -314,8 +320,8 @@ common_start: el2: PRINT("- Xen starting at EL2 -\r\n") - /* Zero BSS On the boot CPU to avoid nasty surprises */ - cbnz x22, skip_bss + /* Zero BSS only when requested to avoid nasty surprises. */ + cbnz x26, skip_bssComparing the original comment here with both this and the earlier hunk, I think the intended meaning is lost. Zeroing the BSS on secondary CPUs is certainly a bug, not a nasty surprise. What I think the original comment is meaning to say is "the BSS should have been zeroed already, but let's better not rely on that".
This is not the original meaning. On non-EFI setup BSS will not be zeroed before hand as the loader of Xen does not know the size of BSS.
> Another aspect is whether this original meaning of
the comment actually holds on ARM, since the Xen image is not an ELF binary (only xen.axf is).
Cheers, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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